RN38, Takasaki, Japan
Thumbnail profile: Takasaki
Situated on the Kanto Plain approximately 100 km northwest of Tokyo, Takasaki City covers an area of 330 km². It is a vibrant urban centre that embraces both the downtown commerce and industry and protects the natural peace and tranquility found in the rural Kurabuchi district. In January 2006 Takasaki City merged with other towns, forming the current city that is home to approximately 320,000 people.
Its proximity to Tokyo, only 50 minutes by bullet train, makes the city a strategic hub for transport and commerce. The city is also home to the Takasaki Advanced Radiation Research Institute and JAERI, the Japan Atomic Energy Research Institute, on the eastern outskirts of the city.
History and Geography
The remains of many ancient communities have been uncovered in Takasaki, proving that people thrived in the area more than 1,400 years ago. During the Edo period (1600-1868), Takasaki's role as a castle town led to an influx of merchants and an increase in the population.
Following the Second World War, Takasaki continued to grow as an industrial city with an extensive transportation system. Japan’s sophisticated bullet train lines make the city a gateway to the entire prefecture, as well as to the Sea of Japan and to the Japanese Alps. Takasaki City nurtures an international society where both the environment and city’s citizens co-exist in harmony together.
The IMS radionuclide station RN38 is located inside the premises of the Takasaki Radiation Chemistry Research Establishment of JAERI (Japan Atomic Energy Research Institute) on the town’s eastern outskirts. This location is just nine km away from the coordinates originally established by the Treaty and was approved by the CTBTO.
A dedicated building was erected solely to host IMS equipment, including future Noble Gas equipment (see below). The building is within walking distance of the offices of the local station operator who is a JAERI staff member. The JAERI laboratory area is fenced off and of restricted access.
The Fukushima Power Plant Accident
The 11 March 2011 earthquake off the Japanese coast and the ensuing tsunami tragically killed tens of thousands of people and left the Fukushima power plant severely damaged. According to Japanese authorities, the CTBTO’s seismic and hydroacoustic stations in the region helped them to issue tsunami warnings within a few minutes, thus allowing many people to escape the tsunami.
Located around 250km to the southwest, RN38 is the IMS station closest to the Fukushima power plant. The station was one of the first IMS radionuclide stations to register radioactive particles such as Iodine-131 and Caesium-137 as well as the radioactive noble gas Xenon-133 emitted by the stricken plant. The station itself was affected by power outages shortly after the earthquake. Read more about the CTBTO’s Fukushima-related measurements.
Radionuclide Station Profile
RN38 is an automatic station of the RASA type—that is, a Radionuclide Aerosol Sampler and Analyzer—developed by the US company Veridian. It is a fully integrated, automated system for monitoring airborne radionuclides and consists of an air sampler with an operational airflow rate of 1000 m3 h-1 with a frequency controller that keeps the operational airflow rate constant during sampling time. The airflow rate indicates the minimum amount of air that passes through the filter. The more air that passes through, the better the station's sensitivity. This air sampler inlet is located on the roof of the dedicated building.
The meteorological system on the station’s roof is connected to the RASA computer system and measures precipitation, air temperature, humidity and pressure, wind speed and wind direction.
Certification, Testing and Evaluation
The site survey was performed by JAERI and completed in August 1998. Infrastructure preparation was contracted to JAERI while the installation of the automatic radionuclide equipment was contracted to Veridian. Station installation was completed by January 2003 and data has been transmitted on a regular basis since then. After a five-month initial testing period in 2003, the station started sending data to the CTBTO’s IDC on 25 August 2003.
The station visit took place in October 2003 and RN38 was found to be well installed and well operated. Data availability had been at a record 100% since November 2008, well exceeding the required 95%. Thus, RN38 was formally certified on 6 February 2004.
Takasaki is one of ten IMS monitoring facilities in Japan. They are connected via the country’s National Data Centre (NDC) in Tokyo to the CTBTO’s International Data Centre (IDC) in Vienna, Austria. The other facilities are one primary and five auxiliary seismic stations, one hydroacoustic station, two radionuclide stations and one radionuclide laboratory.
International Noble Gas Experiment (INGE)
In addition, RN38 at Takasaki is one of the stations participating in the International Noble Gas Experiment (INGE), which was established in 1999 to test the measuring of radionuclide noble gases released by nuclear explosions.
In January 2007 Takasaki’s INGE system, which uses Sweden’s SAUNA—Swedish Unattended Noble gas Analyzer—became operational.